547 research outputs found
The beam modelling of the hawkmoth wing structure
No full textHawkmoth wings consist of veins and membrane elements that undergo large deformations while moving through the air. The intention of this paper is to create an Euler-Bernoulli beam that can model the complex structure of a hawkmoth forewing. The beam undergoes bending and torsion, and its modal analysis and deformation data are validated against those of the wing structure created based on the finite-element method and a biological wing. A multibody dynamics approach is employed to model the deformation of the beam wing when it oscillates at the frequency of an actual hawkmoth
Multiscale modeling of adsorption-transport-mechanical coupling in coal gas reservoirs : enhanced recovery by CO₂ injection
No full textLe gaz de charbon est une ressource énergétique dont l'exploitation peut être accélérée par injection de gaz carbonique (CO₂) combinant ainsi production de méthane (CH₄) et stockage du gaz carbonique produit par sa combustion. La structure du réservoir est considérée comme un milieu à double porosité avec des fractures naturelles (cleats) et une matrice contenant une phase solide et des nanopores (de taille inférieure à 2 nm) où le gaz est stocké par adsorption sur la paroi solide. Le CO₂ est plus facilement adsorbé que le CH₄. Un modèle théorique multiéchelle combinant adsorption, transport et poromécanique du réservoir est développé. À la plus petite échelle, les molécules de gaz sont considérées comme des sphères dures interagissant par un potentiel de Lennard-Jones. Une nouvelle méthode numérique utilise la théorie de la fonctionnelle de densité (DFT) et la théorie fondamentale de la mesure (FMT) pour calculer la distribution des densités moléculaires d'un mélange de gaz pour une géométrie quelconque des nanopores. La paroi solide exerce un potentiel extérieur répulsif à très courte distance et attractif à plus grande distance sur les molécules de gaz. À partir des distributions moléculaires des gaz, la force de solvatation exercée par la phase fluide sur la surface des nanopores est calculée précisément. La méthode de l'homogénéisation asymptotique permet de passer de l'échelle du nanopore à l'échelle microscopique et d'obtenir la réponse de la matrice de charbon. Le modèle poroélastique de Biot est modifié par la force de solvatation qui agit comme le principal facteur gouvernant le gonflement ou la contraction de la matrice. Les équations moyennes de conservation de la masse des deux gaz (CH₄ et CO₂) dans la matrice prennent en compte les phénomènes d'adsorption caractérisés par des coefficients de partition et une diffusion effective de type Knudsen. Une seconde homogénéisation vise à obtenir la loi macroscopique à l'échelle du réservoir en combinant le réseau de cleats et la matrice solide. Le contact à l'interface matrice-cleats est caractérisé par la loi hyperbolique de Barton-Bandis qui modifie la rigidité effective ainsi que la perméabilité du réservoir. Après homogénéisation, le réservoir est un milieu hétérogène et anisotrope du fait de la structure des cleats et de la variation spatiale de la pression du fluide. Une équation moyenne macroscopique pour la diffusion des gaz dans la matrice et le transport gaz-eau dans les cleats est développée en considérant l'échange de masse entre la matrice et les cleats gouverné par l'approximation de Warren et Root. Des simulations numériques démontrent la corrélation cruciale entre les distributions de pression de gaz, l'ouverture des cleats et la rigidité du réservoir. L'injection de CO₂ améliore significativement la production de CH₄. Elle permet le stockage souterrain de CO₂ contribuant à réduire les émissions de gaz à effet de serre.Coal seam gas is an energy resource whose exploitation can be enhanced by injectingcarbon dioxide (CO₂), thus combining the production of methane (CH₄) and the storage of carbon dioxide produced by its combustion. The structure of the reservoir is considered to be a double-porosity medium with natural fractures (cleats) and a matrix containing a solid phase and nanopores (less than 2 nm in size) where the gas is stored by adsorption on the solid wall. CO₂ is more easily adsorbed than CH₄. A multiscale theoretical model combining adsorption, transport and reservoir poro-mechanics is developed. At the smallest scale, the gas molecules are considered as hard spheres interacting through a Lennard-Jones potential. A new numerical method uses Density Functional Theory (DFT) and Fundamental Measure Theory (FMT) to calculate the distribution of molecular densities of a mixture of gases for any nanopore geometry. The solid wall exerts an external potential that is repulsive at very short distances and attractive at longer distances on the gas molecules. From the molecular distributions of the gases, the solvation force exerted by the fluid phase on the surface of the nanopores is precisely calculated. The asymptotic homogenization method is performed to upscale the nanopore-scale model and to obtain the response of the coal matrix at the microscale. The Biot poroelastic model is modified by the solvation force, which acts as the main factor governing matrix swelling or contraction. The average mass conservation equations for the two gases (CH₄ and CO₂) in the matrix take into account adsorption phenomena characterized by partition coefficients and an effective Knudsen-type diffusion. A second homogenization aims at obtaining the macroscopic law at the reservoir scaleby combining the cleats network and the solid matrix. The joint stiffness at the matrix-cleats interface is characterized by the hyperbolic Barton-Bandis law, which modifies the effective stiffness and the permeability of the reservoir. After homogenization, the reservoir is a heterogeneous and anisotropic medium due to the structure of the cleats and the spatial variation of the fluid pressure. A macroscopic average equation for gas diffusion in the matrix and gas-water transport in the cleats is developed by considering the mass exchange between the matrix and the cleats governed by the Warren and Root approximation. Numerical simulations illustrate the crucial correlation between gas pressure distributions, cleat opening and reservoir stiffness. CO₂ injection significantly improves CH₄ production and enables a underground storage of CO₂, which contributes to reducing green-house gas emissions
Enhancement of germination and growth of direct-seeded rice through seed priming
No full textA screenhouse study to prove that seed priming can increase the weed suppressive ability of rice through the improvement of early emergence and growth of rice was conducted. Seed priming with 2% KNO3, 2% CaCl2, 2% NaCl and 2% KCl increased the aboveground biomass of rice, while reductions in weed biomass were observed. Seed priming with 100 ppm of GA3, 2% KNO3, 2% KCl, 2% CaCl2, 2% NaCl, and water for 24 h and 48 h improved shoot development and increased total plant biomass under laboratory condition. Seed priming with water for 24 h and 48 h, 2% KNO3, 2% CaCl2, 2% NaCl, and 2% KCl using Mestiso 21, IR64, and NSIC Rc222 rice varieties improved the plant height, number of leaves, tillers and rice biomass, specifically in Mestiso 21 and IR64. With IR64, seed priming with 2% CaCl2, was found to be the best treatment in terms of biomass accumulation. On the other hand seed priming with water for 24 h and 2% KCl in Mestiso 21, and water for 48 h, 2% NaCl and 2% KNO3, in NSIC Rc222 were the best treatments in terms of seedling biomass accumulation. Hence, specificity of seed priming treatments among rice varieties was observed. Interaction of seed priming treatments with seed burial depths in soil revealed that, emergence percentage, tillers, plant survival, and biomass were reduced, while specific leaf area (SLA) relatively increased at 3 cm burial depth compared to 1 and 2 cm burial depths. Within 1-3 cm burial depths, seeds primed with 2% KNO3 CaCI2 produced the highest shoot and total biomass in rice seedlings, promoted early emergence, improved emergence percentage, germination index (GI), and tillering, but reduced the mean germination time (MGT). Other seed priming treatments that were found to be effective based on the above parameters were seed priming with 2% KCI, water for 24 h and 48 h and 2% NaCl. Generally, the hormones (growth regulators) used increased the emergence rate, but reduced the MGT of seedlings at 14 days after sowing (DAS). Taller seedlings were observed in the treatment using gibberellic acid (GA3) and kinetin. Seeds primed with 25, 50 and 100 ppm kinetin and 25 ppm GA3 improved the total aboveground and total rice seedling biomass (+ root), and leaf area (LA). Seed priming with 50 ppm GA3, and 100 ppm GA + Km improved the total aboveground and total rice biomass. Hormonal priming with 100 ppm kinetin was the best seed priming treatment, wherein seedling emergence and vigor production of leaves, and biomass accumulation were enhanced with the early stages of rice growth up to the tillering stage
Distributed and Secure Social Network Mobile Application
No full textAs one of the twenty-first century greatest invention, online social network (OSN) is now the central information hubs of million lives, storing and controlling data flow of millions tetra bytes, changing the way information is generating, searching and sharing among people. However, due to the more and more dependence of people to some OSN providers, the data of users are violated and manipulated by providers publicly and aggressively. Many researches recently pinpoint that decentralizing and mobile is inevitable trend of OSN. In this thesis, we explore the neat requirements of DOSN in mobile context and propose a solution satisfying them. We first examine potential weakness and problems in some novel DOSN solutions. Thereafter, the deployment of identity-based cryptography and free cloud storage service is introduced to remedy the existing challenges in existing solutions. In addition, we developed proof-of-concept implementations for the system with a clear API and expandable abilities. The experimental evaluation on the system shows that the approach of using identity-based cryptography for privacy enhancement and identity and trust management is feasible in mobile context. Moreover, the free storage clouds assists content serving well and hence reduces energy and computing resource spent on peer-to-peer mobile networks without adding extra cost
Ghost Kitchen Location Problem for Meal Delivery Services
No full textMeal delivery are a key part of on-demand logistics in cities worldwide. Ghost kitchens (“delivery-only
kitchens”) have emerged as facilities for preparing and distributing meals to meet online demand.
This thesis develops an actor-classification framework covering ghost kitchens, platforms, couriers,
and customers. Despite their rise, research on ghost kitchens remains limited, particularly regarding
courier behaviour, on-demand delivery and location optimisation.
Couriers on e-bikes, bikes, or scooters collect from ghost kitchens and deliver to one or more
customers. Since delivery speed depends on kitchen location, site selection is strategically important.
It affects private-sector profitability through delivery efficiency and demand fulfillment and influences
public planning through zoning, infrastructure, and urban policy. Demand randomness and order
variability are key features. Entropy maximisation leads to a Markov model that reproduces pick up,
delivery frequencies and mean delivery time. Key indicators such as mean and variance of delivery
times are derived from model parameters. The model is irreducible, ensuring a unique steady state.
Two parameter estimation methods are proposed: one uses an urgency input to produce delivery
time. The model is calibrated using a public Grubhub dataset and validated with a likelihood ratio
test.
The model also supports street network trip assignment and when combined with a route choice
model, estimates demand for bike lanes or signals. This thesis examines optimal kitchen location
using an entropy-based derivation. Grid search shows how relocation affects delivery time and
demand. Two solution methods are tested: a modified Weiszfeld algorithm and an Adaptive Step
Size Gradient (ASG) method. ASG yields better delivery times and demand outcomes. The thesis
offers practical guidance for kitchen siting and represents a novel contribution by optimising dynamic
pickup and delivery using a Markov model of courier behaviour
Emulated Autoencoder: A Time-Efficient Image Denoiser for Defense of Convolutional Neural Networks against Evasion Attacks
No full textThesis (Master's)--University of Washington, 2022As Convolutional Neural Networks (CNN) have become essential to modern applications such as image classification on social networks or self-driving vehicles, evasion attacks targeting CNNs can lead to damage for users. Therefore, there has been a rising amount of research focusing on defending against evasion attacks. Image denoisers have been used to mitigate the impact of evasion attacks; however, there is not a sufficiently broad view of the use of image denoisers as adversarial defenses in image classification due to a lack of trade-off analysis. Thus, image denoisers' costs, including training time, image reconstruction time, and loss of benign F1 scores of CNN classifiers, are explored in this thesis. Additionally, Emulated Autoencoder (EAE), which is the proposed method of this thesis to optimize trade-offs for high volume classification tasks, is evaluated alongside state-of-the-art image denoisers in the gray-box and white-box threat models. EAE outperforms most image denoisers in both the gray-box and white-box threat models while drastically reducing training and image reconstruction time compared to the state-of-the-art denoisers. As a result, EAE is more appropriate for securing high-volume classification applications of images
On the Poisson variate with beta prior distribution and a numerical method in estimating the resulting unconditional distribution
Get PDFA discrete distribution arises from a Poisson distruibution with parameter A, when the distribution of A itself is of the form cA(a-1)(b-A)(B-1) Ae(C,b), where o is sa scaling factor and a,B,b are strictly positive parameters. However, the functional for of the resulting unconditional distribution is not particularly tractable, hence the study of the statistical properties of the unconditional distribution is limited in the study of its mean and its variance. In regards to the modeling of a real situation, an estimation procedure of the parameters involved in cA(a-1)(b-A) (B-1) is discussed and a closed form of the probability distribution is derived. In addition, when accuracy is desired a numerical analysis of the probability distribution is also presented. The development of the results is continued in Appendix A, as a preparation in computerizing the calculation. Finally, an application to real data is discussed for the purpose of illustrating the model.Approved for public release; distribution is unlimited.Second Lieutenant, Vietnamese Armyhttp://archive.org/details/onpoissonvariate109451673
Tien jaar IFRSs in de Europese Unie: tijd voor een mentaliteitsverandering
No full textDit jaar is het tien jaar geleden dat de International Financial Reporting Standards (IFRSs) in de Europese Unie kracht van wet kregen. Op basis van een uit 2002 daterende Europese verordening ? de zogenoemde IASverordening ? moeten beursgenoteerde ondernemingen in de Europese Unie met ingang van boekjaar 2005 hun geconsolideerde jaarrekening verplicht opstellen in overeenstemming met de IFRSs. Het doel van de introductie van de IFRSs was het creeren van een gelijk speelveld in de Europese Unie op het gebied van de externe .nanci?le verslaggeving om zodoende oneerlijke concurrentie tussen de lidstaten te voorkomen en de ef.ci?nte van de Europese kapitaalmarkt te bevorderen
sj-docx-1-npx-10.1177_1934578X231157145 - Supplemental material for Chemical Constituents From the Marine Microalgae <i>Thraustochytrium pachydermum</i>
No full textSupplemental material, sj-docx-1-npx-10.1177_1934578X231157145 for Chemical Constituents From the Marine Microalgae Thraustochytrium pachydermum by Nguyen Thi Thu Thuy, Hoang Thi Minh Hien, Nguyen Cam Ha and
Le Thi Thom, Dang Diem Hong, Nguyen Van Thinh,
Nguyen Trong Dan, Nguyen Dang Hoi, Vu Thi Loan, Hoang Duc Quang, Dan Thi Thuy Hang, Phan Van Kiem, Nguyen Tien Dat, Nguyen Xuan Nhiem in Natural Product Communications</p
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